libvpsc/pairingheap/PairingHeap.h

/*
 * No promises about correctness.  Use at your own risk!
 *
 * Authors:
 *   Mark Allen Weiss
 *   Tim Dwyer <tgdwyer@gmail.com>
 *
 * Copyright (C) 2005 Authors
 *
 * Released under GNU LGPL.  Read the file 'COPYING' for more information.
 */
#ifndef PAIRING_HEAP_H_
#define PAIRING_HEAP_H_
#include <stdlib.h>
#include <fstream>
// Pairing heap class
//
// CONSTRUCTION: with no parameters
//
// ******************PUBLIC OPERATIONS*********************
// PairNode & insert( x ) --> Insert x
// deleteMin( minItem )   --> Remove (and optionally return) smallest item
// T findMin( )  --> Return smallest item
// bool isEmpty( )        --> Return true if empty; else false
// bool isFull( )         --> Return true if empty; else false
// void makeEmpty( )      --> Remove all items
// void decreaseKey( PairNode p, newVal )
//                        --> Decrease value in node p
// ******************ERRORS********************************
// Throws Underflow as warranted


// Node and forward declaration because g++ does
// not understand nested classes.
template <class T>
class PairingHeap;

template <class T>
std::ostream& operator<< (std::ostream &os,const PairingHeap<T> &b);

template <class T>
class PairNode
{
    friend std::ostream& operator<< <T>(std::ostream &os,const PairingHeap<T> &b);
    T   element;
    PairNode    *leftChild;
    PairNode    *nextSibling;
    PairNode    *prev;

    PairNode( const T & theElement ) :
            element( theElement ),
        leftChild(NULL), nextSibling(NULL), prev(NULL)
        { }
    friend class PairingHeap<T>;
};

template <class T>
class Comparator
{
public:
    virtual bool isLessThan(T const &lhs, T const &rhs) const = 0;
};

/**
 * Pairing heap datastructure implementation.
 *
 * Based on example code in "Data structures and Algorithm Analysis in C++"
 * by Mark Allen Weiss, used and released under the LGPL by permission
 * of the author.
 */
template <class T>
class PairingHeap
{
    friend std::ostream& operator<< <T>(std::ostream &os,const PairingHeap<T> &b);
public:
    PairingHeap( bool (*lessThan)(T const &lhs, T const &rhs) );
    PairingHeap( const PairingHeap & rhs );
    virtual ~PairingHeap( );

    bool isEmpty( ) const;
    bool isFull( ) const;
    int size();

    PairNode<T> *insert( const T & x );
    const T & findMin( ) const;
    void deleteMin( );
    const T extractMin( ) {
        T v = findMin();
        deleteMin();
        return v;
    }
    void makeEmpty( );
    void decreaseKey( PairNode<T> *p, const T & newVal );
    void merge( PairingHeap<T> *rhs )
    {
        PairNode<T> *broot=rhs->getRoot();
        if (root == NULL) {
            if(broot != NULL) {
                root = broot;
            }
        } else {
            compareAndLink(root, broot);
        }
        counter+=rhs->size();
    }

    const PairingHeap & operator=( const PairingHeap & rhs );
protected:
    PairNode<T> * getRoot() {
        PairNode<T> *r=root;
        root=NULL;
        return r;
    }
private:
    PairNode<T> *root;
    bool (*lessThan)(T const &lhs, T const &rhs);
    int counter;
    void reclaimMemory( PairNode<T> *t ) const;
    void compareAndLink( PairNode<T> * & first, PairNode<T> *second ) const;
    PairNode<T> * combineSiblings( PairNode<T> *firstSibling ) const;
    PairNode<T> * clone( PairNode<T> * t ) const;
};

#include "PairingHeap.cpp"
#endif